The long term objective is to locate the brain stem neurons which generate the respiratory pattern in the cat. Neurophysiological techniques and signal analyses will be applied to investigate the links between the high frequency synchrony (90 Hz) seen in the respiratory motor nerves and the central respiratory pattern generator in the brain stem. The 90 Hz inspiratory signal will be pursued upstream to its source, which we postulate is the central respiratory pattern generator. Focal cooling and warming will determine whether the high frequency synchrony is a global or local property of the respiratory neuronal network. Focal temperature effects will identify sites for exploration with microelectrodes to locate respiratory pattern generator neurons. The extent to which pulmonary stretch receptors can affect the power spectral densities of the inspiratory activity of respiratory neurons will be investigated. The physiological significance of the potential feedback loop provided by the mechanical coupling of airway smooth muscle and pulmonary stretch receptors under normal and pathological conditions will be determined. The coherence spectra for the phrenic nerve and the contralateral diaphragmatic electromyogram in decerebrate cats will be computed to determine the extent to which the neural signals influence the power spectra of the diaphragmatic EMG.